Control system for the injection of fuel into internal combustion engines

ABSTRACT

In order to obtain constancy of throughput for the different injectors of an internal combustion engine, the valve is inserted between a supply of fuel and the mechanical injectors is a three way valve connected respectively with the output of the supply, with the injectors possibly through a sequential distributor and with a return to the supply. An electromagnet controlled by electric signals attracts a piston normally connecting the supply output with the return to the supply so as to connect during the desired period the supply output with the injector systems. The three ways of furthermore transiently interconnected at the beginning and at the end of each energization, so as to prevent excess pressure.

United States Patent Monpetit et al. 51 Apr. 24, 1973 [541 CONTROLSYSTEM FOR THE [56] References Cited KNJECTKON OF FUEL INTO INTERNAL SCOMBUSTION ENGINES UNlTED TATES PATENTS [75] Inventors: Louis A.Monpetit, L Etang la Ville; g" ?y----{- -i --l23/I39 E Jurg Schneider;Herve Gueret 3 516 395 6/1970 aim I. of Versallles; Adveme"! 3,490,4251/1970 Bassotetal ..123/139 R Pans; Georges R. Sallot, Elizabethville;Jean-Pierre Paul Assignee:

Filed:

Appl. No.:

Jourde, Villennes S/Sienne; J. W. Ufnaleski, Mantes la Ville, all ofFrance Societe Des Procedes Modemes Dlnjection Sopromi, Les Mureaux,France Apr. 21, 1971 Foreign Application Priority Data 123/139 R, 139AM, 139 E Primary Examiner-Laurence M. Goodridge Attorney-Kenyon &Kenyon Reilly Carr & Chapin [5 7 ABSTRACT In order to obtain constancyof throughput for the different injectors of an internal combustionengine, the valve is inserted between a supply of fuel and themechanical injectors is a three way valve connected respectively withthe output of the supply, with the injectors possibly through asequential distributor and with a return to the supply. An electromagnetcontrolled by electric signals attracts a piston normally connecting thesupply output with the return to the supply so as to connect during thedesired period the supply output with the injector systems. The threeways of furthermore transiently interconnected at the beginning and atthe end of each energization, so as to prevent excess pressure.

10 Claims, 3 Drawing Figures PATENTEDAFRZMUB 7 3,728,989

SHEH 3 OF 3 L. MONPETIT HGUE/QET J. P. JOURDE 5. SHLLOT d. SCHNEIDERJ.YUFNAL.EWSKI F? ADV NIER,

CONTROL SYSTEM FOR THE lNJECTlON OF FUEL llNTO INTERNAL COMBUSTIONENGINES The present invention has for its object a fuel injecting systemfor internal combustion engines. It has already been proposed in thisfield of application to control the injection by means ofelectromagnetically controlled injectors located in the immediatevicinity of and on the upstream side of the admission valves in the caseof an indirect injection and directly into the engine cylinder head inthe case of a direct injection. Each electromagnetic injector portionsout the fuel into the corresponding cylinder upon receipt of an electriccontrolling signal the duration of which is defined by conventionalelectronic means governed by the operative parameters of the engine.

Whereas there is no great difficulty in the production of an electriccontrolling signal corresponding to the actual requirements of theengine, it is a very difficult matter to obtain an amount of injectedfuel which remains identical for a given injector and for a givensignal. As a matter of fact, the allowances in size in the manufactureof the injector lead to modifications in the path of the injector needleand in the cross-sectional area afforded for the passage of fuel andalso to modifications in the magnetic properties and consequently eachset of injectors intended for use with a same engine must be gauged, andthe injectors for use with a same engine must be gauged, and theinjectors must be adjusted by suitable means with a view to obtainingcharacteristic properties very near one another for the differentinjectors, the accuracy required approximating 1 percent.

It has already been proposed to remove these drawbacks by resorting to asingle electromagnetic measuring valve connected with simple mechanicalinjectors, either directly or with the interposition of a rotarydistributor providing for sequential injectors following the sequenceofignitions.

However, this solution was not satisfactory since the uniformdistribution of the throughput between the mechanical injectors was notproperly ensured in the case of a direct connection without'anyintermediate distributor. Furthermore, the injection was performed underunfavorable conditions since the pipes leading from the measuring valvesto the injectors remained subjected to pressure after the closing of themeasuring valve, which resulted in uncontrolled leaks through theinjectors.

The present invention has for its object to cut out these drawbacks andit covers an injection controllay system feeding fuel directly orinderectly into internal combustion engines. According to the invention,an electromagnetic measuring valve adapted to receive an electric signalof a duration varying with the operative conditions of the engine isinserted between a supply of fuel under pressure and mechanicalinjectors of the flap valve or needle type as well known in the art. Thenovelty of the invention resides in that the measuring valve is athree-way valve of which one way is connected with the supply of fuelunder pressure, the second way is connected with the mechanicalinjectors directly or through the agency of a sequential distributor andthe third way is connected with a fuel-returning channel which is keptunder a pressure lower than the gauged pressure of the injectors, saidmeasuring valve being designed in a manner such that the three ways areinterconnected each time an electric signal begins or ends itsactuation.

According to further developments of this inventive idea, various otherimprovements are possible, to wit the member closing the three-way valveis constituted by a hollow annular piston sliding between two extremepositions inside the valve body in which it is guided fluid-tightly,said position being provided with a terminal ridge cooperating for oneextreme position of the piston with a frustoconical seat formed in thevalve body while the fuel under pressure is fed into an annular spaceextending between said frustoconical seat and the surface guiding thepiston inside the valve body and the output of the fuel towards theinjectors starts from a bore extending axially of the frusto-conicalseat, the end of the piston opposed to its terminal ridge being rigidwith the movable armature of the controlling electromagnet and beingprovided with a second ridge cooperating for the other extreme positionof the piston with a second frustoconical seat, the inside of the pistonbeing connected with the output leading to the injectors and the annularspace between the second frustoconical seat and the body of themeasuring valve opening into the fuel-returning channel;

the diameters of the annular piston and of the ridges thereon areselected so as to provide a complete or substantially complete hydraulicbalance for the piston;

the second frustoconical seat is rigid with a cylindrical memberslidingly carried inside the piston and acting as a bearing for one endof a return spring with the interposition of an adjusting screw, whilethe other end of the return spring rests on a dished part rigid with thepiston;

the valve body rests on a flanged support the central section of whichis recessed so as to be connected with the supply of fuel said recessbeing closed by a diaphragm the peripheral edge of which is held fast bya cover screwed onto the flanged support with the interposition of aspring blade between the diaphragm and the cover, so that the spacedefined by the recessed section and the diaphragm forms a hydraulicpressure accumulator;

the support carrying the valve body includes a flange provided withrecesses housing as many electromagnets as there are injectors, saidelectromagnets registering with corresponding output connections formedin a detachable cover while their disc-shaped cooperating electromagnetsand output connections in the recesses connected with the inside of thepiston of the measuring valve and forming a sequential distributor;

the stationary electromagnet armature or armatures forms a tore-shapedmember of ferromagnetic material, the cross section of which is that ofan inverted U, said member housing the energizing winding, said torebeing slotted radially so as to cut off the eddy currents and beinghoused in its turn in a part rigid with the valve body with theinterposition of a sheet of insulating material and/or a fuel-filledgap;

the parts in which the stationary and movable parts are housed aresubjected to a truing along their cooperating surfaces and the positionof the parts when assembled and maximum and residual gap widths areadjusted by means of shims inserted between the surfaces registeringwith each other and also underneath the abutments defining the ends ofthe piston stroke.

By way of example and in order to further the understanding of thefollowing description of an embodiment of the invention, reference shallbe made to the accompanying drawings whereof:

FIG. 1 is a diagrammatic view of an injection plant according to theinvention.

FIG. 2 is a diagrammatic sectional view of a measuring valve providedwith an accumulator of fluid pressure.

FIG. 3 is a diagrammatic sectional view of a measuring valve providedwith a sequential electromagnetic distributor.

Turning to FIG. 1, it is apparent that the engine 1 includes an inputmanifold 51 associated with the individual pipes opening into thedifferent engine cylinders through conventional mechanical injectors,return flap valves or a needle valve. The fuel is sucked out of thecontainer 46 by the pump 50 and delivered into the threewayelectromagnetic measuring valve 3 through the filter 49. The excess fuelreturns into the container 46 under control of a pressure regulator 48while a pressure accumulator 47 which may, if required, form a unit withthe measuring valve 3 is also provided. The measuring valve is connectedwith an input channel 3a, with a liquid output channel wherein theliquid is subjected to a modulated pressure 3b leading to the injectors4 either directly or else through a sequential distributor 9 which maybe controlled mechanically. A pulse transmitter 2 controlled by therotation of the engine is adapted to release the electronic system 5producing the signal controlling the measuring valve 3 and actuating thedistributor 9 to define sequentially the operation of the injectors.Said electronic system 5 produces, as well-known in the art, an electricsignal under control of the operative conditions of the engine, saidsignal adjusting the amount of fuel to be injected by adjusting theduration of the opening periods of the channels 3a and 3b controlled bythe measuring valve 3. Obviously, the injectors may be designed in amanner such that they provide a direct injection into the combustionchamber of the engine instead of resorting to an indirect injection asin the case illustrated, this modification remaining within the scope ofthe invention. Electric energy is fed to the electronic system 5 by thesupply 53 under control of the switch 52.

Turning now more particularly to FIG. 2, it is'apparent that themeasuring valve 3 is associated with the hydraulic accumulator 47 andforms a unit therewith. The body 6 of the measuring valve includes aconnection for the channel 3a feeding liquid under pressure and openinginto a recess 6f formed in the pedestal or flanged support 61' and italso includes connections for the fuel output channel 3b leading to theinjectors, only one of last mentioned connections being illustrated. Theconnection for the channel 30 returning the liquid towards the containerforms part of an upper section 7 rigidly secured to the valve body 6 bythe flanged nut 9. Said upper section 9 encloses the electromagnet 12-13controlling the movements of the annular piston 10. Said electromagnet12, 13 of an annular shape includes a stationary armature, thecross-section of which is in the shape of an inverted U. The winding 13is housed inside the U-shaped armature and is connected with twoterminalsl4 fitted in said upper member through the agency of aninsulating ring 15. It should be remarked that with such an arrangementthe eddy currents which may arise in the stationary armature cannot flowalong a circular path since they are interrupted by one or more radialslots not illustrated which are formed in said stationary armature I2.In order to further cut off any eddy currents, the stationary armature12 is also carefully insulated with reference to the upper section 7which is made of an amagnetic material by an insulating sheet 30illustrated in interrupted lines and by an annular slot 7b which isfilled with fuel and serves as a return passageway for the leaks towardsthe connection 30 through the intermediate oblique bore 70. After theelectromagnet 12, 13 has been positioned inside the upper section 7, thesurface registering with the valve body 6 are subjected to a truingalong a transverse plane.

The electromagnet 12, 13 controls the movement of the annular piston 10which is provided for this purpose with the movable armature 21 which isrigidly secured to the piston as provided by folding back its edge 21aover a corresponding shoulder of the piston. The annular piston 10slides fluidtightly between two extreme positions inside the body 6.Fluidtightness is ensured either by means of a fluidtight packing 16 asillustrated or else by means of a balanced assembly with a very narrowclearance. The stroke of the piston 10 between its extreme positions islimited by the frustoconical sealing surfaces 6a on the body 6 and 11bon the cylindrical inner guiding sleeve-shaped member 11 respectively,while the maximum gap corresponding to the contact between the sealingridge 10b and the frustoconical sealing surface 60 is adjusted by a shim28 inserted between 'the upper section 7 and the body 6 whereas theminimum or residual gap corresponding to the contact between the sealingridge 10a and the frustoconical sealing surface 11b is similarlyadjusted by another shim 2 inserted between the upper section 7 and theguiding member 11. To this end the upper surfaces of the body 6 and ofthe movable armature 21 and also of the guiding member 11 are subjectedto a truing in a transverse plane. Through such a simple machining andassembling, all difficulties as to the machining allowances for thedifferent parts are cut out. By way of exemplification it may bementioned that the maximum gap is of a magnitude of 0.05mm, the strokeof the piston being thus equal to about 0. lOmm.

It is apparent that the hollow cylindrical member 11 slidingly engagesthe annular piston 10 and is carried by it through the return spring 19which rests on the dished member 17 secured by an annulus 18 to theinner surface of the piston while the other end of the spring 19 bearsagainst a shoulder 20b provided on the adjusting screw 20 screwed intothe head of the guiding member 1 The adjustment of the tensioning of thespring 19 may be performed after the measuring valve has been assembled,by introducing a tubular wrench into the reccessed end 11a of theguiding member 11 while a screw driver is introduced into the slot 20aof the screw 20 so as to make the latter turn in the direction requiredfor adjustment. When the piston is in the position illustrated withoutthe electromagnet being energized, the output connection 3b communicateswith the return connection 3c through the oblique bore 6g, the centralbore 6e, the inside of the annular piston 10 and of the innercylindrical member, the clearance 60, the clearance 7b and the obliquebore 7a, so that the injectors are subjected to a low pressure which maybe equal to atmospheric pressure or to say 2 to 3 bars in order toprevent the formation of vapor bubbles in the circuit under the actionof the temperatures developed during operation Such a counter-pressureshould however be lower than the gauged pressure in registry with theinjectors.

When the electromagnet 12, 13 is energized, the movable armature 21 isattracted upwardly and the sealing ridge a on the annular piston 10engages the frustoconical surface 11b whereby the communication betweenthe central bore 62 in the valve body and the return connection 3e iscut off whereas the connection 30 feeding fuel under pressurecommunicates with the output connection 3b and thereby with the injectorsystem through the recess 6f formed in the flanged pedestal 61' of thevalve body 6, the oblique bore 6d in said body, the annular space 6bsurrounding the lower end of the now raised piston, the passage thusafforded between the sealing ridge 10b and the cooperating surface 6a,the central bore 62 in the valve body and'the oblique bore 6g.

Thus, it appears that the injectors receive suddenly liquid underpressure when the electromagnet is energized and this produces aninjection during the period of energization of the electromagnet afterwhich, the electromagnet being deenergized, the pressure returnsspeedily to its original value which produces a clean and quick closingof the injectors; this ensures identity between the throughputs in thedifferent injectors, even if said injectors are to operatesimultaneously for each pressure surge. It should be remarked that thisparticularly remarkable result is achieved'by providing an interconnection between all three connections 3a, 3b, 30 at the beginningand at the end of each energization of the electromagnet 12, 13 when thepassage between the lower sealing ridge 10b and the frustoconicalsealing surface 6a is already open, while the passage between the uppersealing ridge 10a and the cooperating sealing surface 11b is not yetclosed.

In order to maintain the minimum magnetic stress simultaneously with avery short delay for the response of the measuring valve, the piston 10is entirely balanced or substantially so for all the positions assumedby it, provided substantial equality is obtained between the diametersof the upper and lower sealing ridges 10a and 10b on the piston 10. 7

It should be remarked furthermore that the hydraulic accumulator 47forming a unit with the measuring valve 3 is constituted merely by therecess 6f in the flanged pedestal 61 which recess is closed by thedouble diaphragm 23 clamped against said flange 6i by the cover'8engaged by the screws 27. A spring blade 25 urges the diaphragm 23upwardly through the agency of the supporting plate 24 secured to thediaphragm by the central nut and screw system 26. The bore 6e in the fvalve body at the end facing 47 is closed by a plug 22,

so that the accumulator communicates only with the input connection 3awhen the measuring valve is inoperative. Y

Said valve is illustrated at a scale 2:1 and its capacity appears thusas quite remarkable.

FIG. 3 illustrates a measuring valve intended chiefly for Dieselengines. Since Diesel engines are of the direct injection type andrequire therefore sequential injection, said measuring valveincorporates an electromagnetic sequential distributor forming a unitwith it. The actual measuring part of the valve is practically identicalwith that illustrated in FIG. 2 and similar elements carry the samereference numbers. For sake of an easier machining the piston 2 and thehollow cylindrical guiding member 11 are housed in an independent partfitted in the valve body 6.

Fluidtightness is ensured between this inserted part and the body 6 bytore-shaped packings 31, 32. The valve body is provided with radial bore611 connecting the annular clearance 6b between said insert part and thepiston with the annular chamber 5'b between the latter and the actualvalve body 6'; which chamber 6'12 communicates in its turn through abore 6a with the connection 3a feeding fuel under pressure. On the otherhand, the central bore 6e is alined with a bore 3b opening into acentral recess 28'a. The sequential distributor is constituted byelectromagnets including a stationary armature 12 and a winding 13cooperating with a disc-shaped movable armature 21. The electromagnetsare executed in a manner similar to the electromagnets 12,13 of themeasuring valve. In other words, they are fitted in their housings withthe interposition of an insulating sheet 30' along their periphery whilea plug 11, of an amagnetic material is first inserted before the shim29' to allow a truing of the flat lower surface of the valve body 6'.The winding 13 is connected withthe terminals 14' protected by theirinsulating sheaths 15. The movable armature 21 is housed in a recess inthe disc 28 communicating with the central recess 28'a. Said movablearmature 21 is provided with a fluidtight packing 37, so that theconnection 3b is cut off from the central recess 28'a when the movablearmature is at rest and is not attracted upwardly by the energization ofthe electromagnet. The maximum gap is defined by the difference inthickness between the disc 28' and the movable armature 21 whereas theresidual gap is defined by the shim 29. A tore-shaped fluidtight packing36 is providedround the plug 11' which encloses a return spring 19'within an inner recess. The tore-shaped packings 35 ensurefluidtightness between the central recess 28a and the externalatmosphere while a centering sleeve 34 is provided for the positioningof the cover 8 carrying the disc 28' with reference to the flangedpedestal 61' of the valve body.

The electromagnets 12, 13 may be executed very simply and their bulk maybe small since they are energized only outside the injection periods andhave therefore to exert a very slight effort in order to merely attractthe movable armature 21' since no difference in pressure acts on saidmovable armature at the moment of the opening and closing of theentrance of the connection 3b. Thus, even in the case where themeasuring valve 3 is associated with an electromagnetic sequentialdistributor 9, the arrangement is extremely simple and compact, so thatit may be executed at a comparatively low cost price.

What we claim is 1. In a fuel injection system for internal combustionengines of the type that includes a container of fuel,

means for supplying fuel under pressure from the container, a fuelinjector associated with each combustion space of the engine, means forproducing intermittent electric signals synchronized with enginerotation and of a duration depending on the operative conditions of theengine, and a three-way metering valve having an inlet connected to themeans for supplying fuel under pressure, a first outlet connected to thefuel injectors, a second outlet connected to a low pressure return lineto the fuel container, and means for actuating the valve intermittentlyin response to the electric signals to supply variable quantities offuel to the injectors as a function of the duration of each signal, theimprovement wherein the metering valve comprises:

a valve body having an internal chamber;

a first annular valve seat in the chamber;

a second annular valve seat in the chamber, spaced from and facing thefirst seat;

a first passageway opening into the chamber adjacent the outercircumference of the first seat and communicating with the valve inlet;

a second passageway opening into the chamber adjacent the innercircumference of the first seat and communicating with the first outletof the valve;

a third passageway opening into the chamber adjacentthe outercircumference of the second seat and communicating with the secondoutlet of the valve; and

a valve member mounted in fluid-tight relation to the chamber wallbetween the openings of the first and third passageways for movement bythe actuating means from a first position to a second position inresponse to the electric signals, the valve member having first andsecond oppositely-facing circular contact surfaces for sealingengagement respectively with the first valve seat when in the firstposition and with the second valve seat when in the second position, andthe valve member further having a passageway joining the inner sides ofthe first and second circular contact surfaces, whereby the valve memberwhen in the first position permits communication only between the secondand third passageway, when in the second position permits communicationonly between the first and second passageways, and when intermediate thefirst and second positions permits communication between all threepassageways.

2. The fuel injection system of claim 1 wherein the valve actuatingmeans comprises:

an electromagnetic actuator connected to the valve member for moving themember from the first to the second position atthe commencement of eachof the electric signals and I a biasing means for returning the valvemember to the first position at the termination of each of the electricsignals.

3. The fuel injection system of claim 2 wherein the valve chambercomprises a cylinder, thefirst and second valve seats comprisefrusto-conical surfaces at opposite ends of the chamber, and-the valvemember comprises a tubular piston mounted for fluid-tight slidingengagement with the wall of the cylindrical chamber between the openingsof the first and third passageways.

4. The fuel injection system of claim 3 wherein the first frusto-conicalvalve seat is concave; the first circular contact surface of the valvemember comprises an outward-facing edge formed by the intersection ofthe exterior surface of the tubular valve member with the end surface ofthe valve that faces the first seat; and the first and second contactsurfaces have approximately equal diameters, whereby the hydrostaticforces on the valve member are substantially balanced.

5. The fuel injection system of claim 4 wherein the secondfrusto-conical valve seat is convex; the second circular contact surfaceof the valve member comprises an inward facing edge formed by theintersection of the interior surface of the tubular member with the endsurface of the valve member that faces the second valve seat; and theelectromagnetic actuator comprises an electromagnet having a toroidal,radially-slotted ferromagnetic core of U-shaped cross section fixedlymounted within the valve body coaxially with the valve member, anenergizing winding inside the core, and a ferromagnetic annular armatureattached to the outside of the valve member for movement axially towardthe core in response to energization of the magnet winding by theelectric signals.

6. The fuel injection system of claim 5 wherein the biasing meanscomprises:

a first annular shoulder extending inward from the inner surface of thetubular valve member and facing the second valve seat;

a threaded stud mounted coaxially with respect to the second valve seatand having a head with a second annular shoulder facing the firstannular shoulder; and

a compression spring positioned within the tubular valve member andhaving one end bearing against the first shoulder and an opposite endbearing against the second shoulder to urge the valve member toward thefirst position, the threaded stud permitting adjustment of the axialspacing between the first and second shoulders and thereby the forceexerted by the biasing means tending to urge the valve member toward thefirst position.

7. In a fuel injection system for internal combustion engines of thetype that includes a container of fuel, means for supplying fuel underpressure from the container, a fuel injector associated with eachcombustion space of the engine, means for producing intermittentelectric signals synchronized with engine rotation and of a durationdepending on the operative conditions of the engine, and a three-waymetering valve having an inlet connected to the means for supplying fuelunder pressure, a first outlet connected to the fuel injectors, a secondoutlet connected to a low pressure return line to the fuel container,and means for actuating the valve intermittently in response to theelectric signals to supply variable quantities of fuel to the injectorsas a function of the duration of each signal, the improvement whereinthe metering valve comprises:

a valve body having an internal chamber;

a first passageway opening into the chamber and communicating with thevalve inlet;

a second passageway opening into the chamber and communicating with thefirst outlet of the valve;

a third passageway opening into the chamber and communicating with thesecond outlet of the valve; and

a valve member mounted in the chamber for movement by the actuatingmeans in response to the electric signals from a first position in whichit prevents communication between the openings of the first and secondpassageways to a second position in which it prevents communicationbetween the opening to the third passageway and the openings to thefirst and second passageways, the valve member when intermediate thefirst and second positions permitting communication between all threeopenings.

8. The fuel injection system of claim 7 further comprising:

a plurality of recesses in a face of the valve body adjacent the firstoutlet of the valve, the number of recesses corresponding to the numberof injectors in the system;

a cover plate attached in fluidtight relation to the face of the valvebody, the cover plate having a portion spaced from the face of the valvebody to provide an auxiliary chamber enclosing the first outlet and theplurality of recesses, the cover plate having further:

a plurality of auxiliary passageways, each leading from an openingopposite a corresponding recess to a corresponding fuel line connectedwith one of the injectors and a plurality of auxiliary seating surfaces,each surface surrounding the opening corresponding to one of theauxiliary passageways;

a plurality of stationary auxiliary electromagnets, one electromagnetbeing mounted in each recess;

a plurality of magnetic auxiliary armatures, one armature beingpositioned between each electromagnet and the corresponding seatingsurface, each auxiliary armature having a contact surface for sealingengagement with the corresponding seating surface when the armature isin a first position; v

biasing means in each recess for urging each auxiliary armature towardthe first position for preventing flow between the first outlet of thevalve and the corresponding injector; and

a distributor of auxiliary electric signals synchronized with themetering valve electric signals for energizing each auxiliaryelectromagnet in sequence to actuate the corresponding auxiliaryarmature to move to a second position against the force of the biasingmeans, in which position the contact surface is disengaged from theauxiliary seating surface for permitting flow from the means forsupplying fuel under pressure to each injector in turn for the durationof the valve energizing signal.

9. The fuel injection system of claim 8 wherein each auxiliary armaturecomprises:

a fiat ferromagnetic disc having an annular contact surface on one side.10. The fuel injection system of claim 7 further comprising:

a fuel accumulating recess in a surface of the valve body, the recesscommunicating permanently with the first assageway; a flexible iaphragmenclosing the fuel accumulating recess;

a cover plate overlying the diaphragm and fastened to the valve body forurging the edges of the diaphragm into sealing engagement with thesurface of the valve body surrounding the fuel accumulating recess; and

biasing means positioned between the cover plate and the diaphragm forurging the diaphragm away from the cover plate inward toward the fuelaccumulating recess.

1. In a fuel injection system for internal combustion engines of thetype that includes a container of fuel, means for supplying fuel underpressure from the container, a fuel injector associated with eachcombustion space of the engine, means for producing intermittentelectric signals synchronized with engine rotation and of a durationdepending on the operative conditions of the engine, and a three-waymetering valve having an inlet connected to the means for supplying fuelunder pressure, a first outlet connected to the fuel injectors, a secondoutlet connected to a low pressure return line to the fuel container,and means for actuating the valve intermittently in response to theelectric signals to supply variable quantities of fuel to the injectorsas a function of the duration of each signal, the improvement whereinthe metering valve comprises: a valve body having an internal chamber; afirst annular valve seat in the chamber; a second annular valve seat inthe chamber, spaced from and facing the first seat; a first passagewayopening into the chamber adjacent the outer circumference of the firstseat and communicating with the valve inlet; a second passageway openinginto the chamber adjacent the inner circumference of the first seat andcommunicating with the first outlet of the valve; a third passagewayopening into the chamber adjacent the outer circumference of the secondseat and communicating with the second outlet of the valve; and a valvemember mounted in fluid-tight relation to the chamber wall between theopenings of the first and third passageways for movement by theactuating means from a first position to a second position in responseto the elecTric signals, the valve member having first and secondoppositely-facing circular contact surfaces for sealing engagementrespectively with the first valve seat when in the first position andwith the second valve seat when in the second position, and the valvemember further having a passageway joining the inner sides of the firstand second circular contact surfaces, whereby the valve member when inthe first position permits communication only between the second andthird passageway, when in the second position permits communication onlybetween the first and second passageways, and when intermediate thefirst and second positions permits communication between all threepassageways.
 2. The fuel injection system of claim 1 wherein the valveactuating means comprises: an electromagnetic actuator connected to thevalve member for moving the member from the first to the second positionat the commencement of each of the electric signals and a biasing meansfor returning the valve member to the first position at the terminationof each of the electric signals.
 3. The fuel injection system of claim 2wherein the valve chamber comprises a cylinder, the first and secondvalve seats comprise frusto-conical surfaces at opposite ends of thechamber, and the valve member comprises a tubular piston mounted forfluid-tight sliding engagement with the wall of the cylindrical chamberbetween the openings of the first and third passageways.
 4. The fuelinjection system of claim 3 wherein the first frusto-conical valve seatis concave; the first circular contact surface of the valve membercomprises an outward-facing edge formed by the intersection of theexterior surface of the tubular valve member with the end surface of thevalve that faces the first seat; and the first and second contactsurfaces have approximately equal diameters, whereby the hydrostaticforces on the valve member are substantially balanced.
 5. The fuelinjection system of claim 4 wherein the second frusto-conical valve seatis convex; the second circular contact surface of the valve membercomprises an inward facing edge formed by the intersection of theinterior surface of the tubular member with the end surface of the valvemember that faces the second valve seat; and the electromagneticactuator comprises an electromagnet having a toroidal, radially-slottedferromagnetic core of U-shaped cross section fixedly mounted within thevalve body coaxially with the valve member, an energizing winding insidethe core, and a ferromagnetic annular armature attached to the outsideof the valve member for movement axially toward the core in response toenergization of the magnet winding by the electric signals.
 6. The fuelinjection system of claim 5 wherein the biasing means comprises: a firstannular shoulder extending inward from the inner surface of the tubularvalve member and facing the second valve seat; a threaded stud mountedcoaxially with respect to the second valve seat and having a head with asecond annular shoulder facing the first annular shoulder; and acompression spring positioned within the tubular valve member and havingone end bearing against the first shoulder and an opposite end bearingagainst the second shoulder to urge the valve member toward the firstposition, the threaded stud permitting adjustment of the axial spacingbetween the first and second shoulders and thereby the force exerted bythe biasing means tending to urge the valve member toward the firstposition.
 7. In a fuel injection system for internal combustion enginesof the type that includes a container of fuel, means for supplying fuelunder pressure from the container, a fuel injector associated with eachcombustion space of the engine, means for producing intermittentelectric signals synchronized with engine rotation and of a durationdepending on the operative conditions of the engine, and a three-waymetering valve having an inlet connected to the means for supplying fuelunder pressurE, a first outlet connected to the fuel injectors, a secondoutlet connected to a low pressure return line to the fuel container,and means for actuating the valve intermittently in response to theelectric signals to supply variable quantities of fuel to the injectorsas a function of the duration of each signal, the improvement whereinthe metering valve comprises: a valve body having an internal chamber; afirst passageway opening into the chamber and communicating with thevalve inlet; a second passageway opening into the chamber andcommunicating with the first outlet of the valve; a third passagewayopening into the chamber and communicating with the second outlet of thevalve; and a valve member mounted in the chamber for movement by theactuating means in response to the electric signals from a firstposition in which it prevents communication between the openings of thefirst and second passageways to a second position in which it preventscommunication between the opening to the third passageway and theopenings to the first and second passageways, the valve member whenintermediate the first and second positions permitting communicationbetween all three openings.
 8. The fuel injection system of claim 7further comprising: a plurality of recesses in a face of the valve bodyadjacent the first outlet of the valve, the number of recessescorresponding to the number of injectors in the system; a cover plateattached in fluidtight relation to the face of the valve body, the coverplate having a portion spaced from the face of the valve body to providean auxiliary chamber enclosing the first outlet and the plurality ofrecesses, the cover plate having further: a plurality of auxiliarypassageways, each leading from an opening opposite a correspondingrecess to a corresponding fuel line connected with one of the injectorsand a plurality of auxiliary seating surfaces, each surface surroundingthe opening corresponding to one of the auxiliary passageways; aplurality of stationary auxiliary electromagnets, one electromagnetbeing mounted in each recess; a plurality of magnetic auxiliaryarmatures, one armature being positioned between each electromagnet andthe corresponding seating surface, each auxiliary armature having acontact surface for sealing engagement with the corresponding seatingsurface when the armature is in a first position; biasing means in eachrecess for urging each auxiliary armature toward the first position forpreventing flow between the first outlet of the valve and thecorresponding injector; and a distributor of auxiliary electric signalssynchronized with the metering valve electric signals for energizingeach auxiliary electromagnet in sequence to actuate the correspondingauxiliary armature to move to a second position against the force of thebiasing means, in which position the contact surface is disengaged fromthe auxiliary seating surface for permitting flow from the means forsupplying fuel under pressure to each injector in turn for the durationof the valve energizing signal.
 9. The fuel injection system of claim 8wherein each auxiliary armature comprises: a flat ferromagnetic dischaving an annular contact surface on one side.
 10. The fuel injectionsystem of claim 7 further comprising: a fuel accumulating recess in asurface of the valve body, the recess communicating permanently with thefirst passageway; a flexible diaphragm enclosing the fuel accumulatingrecess; a cover plate overlying the diaphragm and fastened to the valvebody for urging the edges of the diaphragm into sealing engagement withthe surface of the valve body surrounding the fuel accumulating recess;and biasing means positioned between the cover plate and the diaphragmfor urging the diaphragm away from the cover plate inward toward thefuel accumulating recess.